Mark Pilant <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Greetings all.
I have managed to find some time to work on my TR-3 and have
made a fair amount of progress.
The first step was to clean off most of the grime, dust, etc.
with Q-tips and (isopropyl) alcohol. Followed by DeoxIT on the
various switch contacts, tube socket contacts, and T/R relay.
BTW, I discovered the blue coloring on the blue filter can be
removed with the alcohol. Fortunately, the bluing was on the
white backing no the actual blue filter. Be careful.
After that came doing all resistance checks. Anything more
than 10% off the table in the manual I investigated. I found
two very curious things. First, pin 7 (6AU6A - VFO cathode) is
shown as 7 ohms in the table, but my meter (Fluke 875 with needle
probes) showed it as open. The original manual I have (from a
different owner) also shows this. I'm not sure if this is OK.
I'm not sure I really want to pull the PTO to trace the circuit.
Second, the first time through, the cathode and grid resistance
measurements of several tubes were vastly different (in both
directions: high and low). Looking into this further, the tubes
all appeared to be in the receive chain. On a hunch, I played
around a but with the T/R relay contacts while measuring the
cathode resistance of V12 (IF amp). It would go from 105 ohms
to 29.7K. What was curious was it wasn't up and down motion of
the relay contact but side to side.
So it looks like my T/R relay needs some serious attention. I
can think of a several of things to try:
1) Clean it again with DeoxIT (by pulling soaked heavy
paper through the contacts).
2) Use a burnisher or very fine grit (1000+) wet/dry
sandpaper. (Like Mark Gilger's "Relay Care" Tech Tip
on WB4FHN's site.)
3) Find a replacement relay. I'm not sure if this is
possible.
Since my TR-3 has an open frame T/R relay, it isn't too surprising
it is dirty. I'm just not sure if I will be able to adequately
clean the contacts. I'm preparing myself to have to remove the
relay to really clean it. I'll also check the armature string
tension as well.
All comments and suggestions welcome.
73
- Mark N1VQW
----------------------------------------------------------------------
Submissions: [EMAIL PROTECTED]
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net
----------------------------------------------------------------------
